Re: [PATCH 24/32] vfs: syscall: Add fsopen() to prepare for superblock creation [ver #9]

On Thu, Jul 12, 2018 at 07:15:05PM +0200, Greg KH wrote:

On Tue, Jul 10, 2018 at 11:44:09PM +0100, David Howells wrote:

quoted

Provide an fsopen() system call that starts the process of preparing to
create a superblock that will then be mountable, using an fd as a context
handle.  fsopen() is given the name of the filesystem that will be used:

	int mfd = fsopen(const char *fsname, unsigned int flags);

where flags can be 0 or FSOPEN_CLOEXEC.

For example:

	sfd = fsopen("ext4", FSOPEN_CLOEXEC);
	write(sfd, "s /dev/sdb1"); // note I'm ignoring write's length arg
	write(sfd, "o noatime");
	write(sfd, "o acl");
	write(sfd, "o user_attr");
	write(sfd, "o iversion");
	write(sfd, "o ");
	write(sfd, "r /my/container"); // root inside the fs
	write(sfd, "x create"); // create the superblock

Ugh, creating configfs again in a syscall form?  I know people love
file descriptors, but can't you do this with a configfs entry instead if
you really want to do this type of thing from userspace in this type of
"style"?

Why reinvent the wheel again?

The damn thing REALLY, REALLY depends upon the fs type.  How would
you map it on configfs?